According to witnesses, Lamar was at Beacher's Madhouse in Hollywood Wednesday night, and he was COMPLETELY WASTED. This comes just after reports of him willing to turn things around for Khloe, including volunteering sobriety tests.

Those who spotted the giant basketballer said he showed up with several guys, went straight to the bar to do shots of Patron, and then drank as much champagne as possible for the next 3 hours.

One source said he was "hammered" while another said it looked purely like an alcohol inebriation, not a drug-fueled one. He stayed until they closed at 2AM!

That's not all, though — at 2:30 AM he was in the valet area asking about the "after party."

It's just such a shame after all the positive stuff we had been hearing!